Ground rod



Nov. 10, 1936. A. J. WAYMAN GROUND ROD Filed Oct. 6, 1954 N m V: A W J T R E B L A w, M MW Patented Nov. 10, 1936 UNITED STATES PATENT OFFICE GROUND ROD Ohio Application October 6,

11 Claims.

My invention relates to ground rods for grounding electric systems, and in particular to rods of the type which are driven into the ground.

In the use of ground rods of this type, after the rod has been driven, only the person who selected the rod and drove it into the ground knows how deep the rod extends. Accordingly, it is not possible for an electrical inspector to determine the depth of the ground rod after it has been driven into the ground. Since the underwriters regulations require that ground rods must be driven into the ground a certain distance in order to secure good contact with permanently moist earth, it is highly desirable that it be possible for the inspector to determine the depth of the ground rod after the rod has been driven and without having to witness the actual driving.

An object of the present invention is to devise a ground rod embodying an indicator element whereby an inspector may determine the length of the ground rod after it has been driven into the ground.

A further object of the invention is to devise an improved construction of ground rod which is easily assembled and which secures a good electrical connection between the driving point and the driving head.

Another object is to devise a ground rod construction in which the force exerted upon the driving head during the driving operation serves to lock the head to the driving tube.

Still another object is to devise a ground rod construction in which the force exerted upon the driving head during the driving operation serves to securely clamp the internal ground conductor in electrical contact with the driving head.

Still another object is to devise an improved method of securing the external grounding conductor to the head of the ground rod.

My invention is illustrated in the accompanying drawing in which:

Figure 1 is an elevational view, partly in section, illustrating one form of ground rod;

Figure 2 is a sectional view taken along the line 2-2 of Figure 1;

Figure 3 is a sectional view taken along the line 33 of Figure 1; and

Figure 4 is an elevational View, partly in section, illustrating a second form of ground rod.

Referring to Figures 1, 2 and 3, the ground rod is formed of a driving tube or pipe I which is made of material having considerable mechanical strength, such as an ordinary galvanized iron pipe of a length sufficient to extend into the ground and into contact with permanently moist 1934, Serial No. 747,218

earth. On the upper end of the driving tube is arranged a driving head 2 formed of material of good electrical conductivity such as copper or brass. The upper half of the driving head 2 is formed of a generally square cross-section as shown in Figure 2, and is provided with a transverse bore id for receiving conductor 4 which connects the driving head to the electrical system to be grounded. On one side of the driving head is mounted a threaded screw 21) adapted to engage the conductor d and force a section of the conductor into a counter-bore 20 formed in the head opposite the screw 2b. The bore 20 is of sufficiently large diameter to permit the conductor 4 to be bent and forced into the bore in the man ner shown in Figure 2 without danger of rupturing the conductor or reducing its cross-sectional area. The screw 21) is of a limited length such that its head comes in contact with the driving head 2 and is locked in position without unnecessary bending of the conductor 4. If desired, a 20 lock washer 211 may be inserted under the head of the screw 21) to prevent the screw from working loose.

The lower section of the driving head 2 is formed as a cylindrical sleeve which surrounds the upper end of the driving tube I, and the bore which forms the sleeve is preferably enlarged at its upper end as shown at 2c in Figure 1. The lower right hand portion of the head 2 is shown cut away to illustrate the construction of the upper end of the rod. Arranged within the upper end of tube 1 are two halves 5a and 5b of a tapered split plug, between which is arranged one end of the internal grounding conductor 6. The conductor 6 is located within V-grooves formed in opposite faces of the split plug 5a5b as shown in Figure 3. At the lower end of the driving tube is arranged a driving point 3 which may be formed of malleable cast iron and is provided with a shank 3a extending into the tube I as shown. The lower end of the internal grounding conductor 6 extends into a bore formed in the shank 3a of the driving point 3, and is securely locked in this shank by means of a screw 3b threaded in the 45 shank and forcing the conductor 6 into the slotted recess 30 as shown in Figure 1. This form of connection is substantially like that described above for connecting the external ground conductor 4 to the driving head 2.

In order to be able to determine the length of the ground rod after it has been driven into the ground, I arrange within the tube a threadlike indicator 1 which, for example, may be a. Wire secured at its lower end to the shank 3a by means of a frangible connection 8, which, in the example shown in Figure 1, may comprise a length of small wire or cord connected between the hook formed on the lower end of the wire 1 and'a hook 8a secured to the shank 3a. The upper end of the indicator wire 1 extends out of the tube through a hole Ia formed just below the driving head 2, and may be provided with a ring la to facilitate withdrawal of the wire from the tube.

Figure 1 illustrates the manner in which the parts are assembled preparatory to driving the rod in the ground. As driving force or impact is applied to the top of driving head 2, the head is forced down against the split plug 5a 5b, which, due to its tapered upper end, causes the upper end of the tube I to flare out and extend into the enlarged bore 26, thus effectively looking the driving head onto the driving tube I. It will be noted also, as the split plug 5a5b is forced into the upper end of tube I, the plug serves to effectively clamp the upper end of the internal grounding conductor 6 to the tube and to maintain good electrical contact between the conductor, the tube, and the driving head. Good clamping or looking together of the head, tube and grounding conductor may be obtained without the use of the enlarged recess 2e adjacent the bottom of the tube bore in the head 2, but the recess will provide a more secure lock between the head and the tube.

In assembling the rod shown in Figure 1, the indicator wire 1 is threaded through the hole la and passed out of the lower end of the tube and attached to the shank 30. by the frangible link 8. The grounding conductor 6 is also threaded through the tube and attached to the shank 3a, and then the shank is forced into the lower end of the tube I. The two halves of the split plug 5a- 5b are then inserted in the open end of tube I, embracing the end of conductor 6. The driving head or cap 2 is then slipped over the upper end of the tube l, and, in order to prevent the assembly from coming apart during shipment, the head may be driven lightly onto the tube.

In using the ground rod of my invention, the electrical contractor receives the rod assembled as shown in Figure l and drives the rod into the ground, leaving the ring la exposed above the ground. When the electrical inspector comes to inspect the installation, he removes the indicator wire by applying a sudden jerk to the ring la, thereby breaking the frangible connection 8, and, by measuring the length of the indicator wire, he will know how deep the rod extends. Should the inspector find that the indicator wire may be withdrawn without exerting any appreciable force upon it, he knows that the ground rod has been tampered with, and may require the installation of a. proper rod. It will be understood that the frangible connection 8 may be formed to require a substantial pull to break the connection before the indicator wire can be removed from the tube. Also, by forming the indicator wire of rather stiff wire it will not be necessary to provide a frangible connection between the lower end of the wire and the shank 3a, and in this case, if the wire does not show any evidence of coiling or bending, but may be removed with a fairly steady pull, the inspector will know that the ground rod extends into the ground approximately the length of the indicator wire. On the other hand, should the inspector experience difficulty in removing the wire from the tube, and finds evidence of bending or coiling of the wire, he will require the installation of a new ground rod.

A second form of ground rod is illustrated in Fig. 4 in which parts corresponding to like parts in Figures 1 to 3 are indicated by like reference numerals. In this arrangement, the driving head 2 is provided with an integral plug 2f which ex tends into the upper end of tube I. The upper end of the internal grounding conductor 6 is ar-- ranged within a groove formed on the outer surface of the plug 2f and is clamped between the plug and the tube l as the plug is forced into the tube I. In order to secure good clamping of the ends of conductor 6, the plug 2 and the shank 3a may be tapered, or the grooves in these elements for receiving the conductor ends may be tapered, with the deep end of the groove located at the end of the plug or shank. The lower end of conductor 6 is likewise arranged within a roove formed in the outer surface of shank 3a and is effectively clamped between the shank and the tube I as the shank is forced into the tube. The lower end of the indicator wire I is secured to the shank 30. by frictional engagement of a short length between the shank and the wall of the tube, only sufficient length of the wire being clamped to permit the withdrawal of the wire by force manually exerted upon the ring la. The arrangement for connecting the external grounding conductor to the head 2 is the same as described in connection with Figures 1 to 3.

While I have shown only two forms of ground rod embodying the main features of my invention, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention. For example, the indicator element I need not be a wire, but it might be formed of any threadlike element such as a stout cord or even a small link chain. Also, various other methods of attaching the indicator element to a part of the rod near the driving point may be used. For example, the end of the wire I may be hooked directly over the hook 8a, and either of these hook elements may be formed of wire sufficiently small so that a sudden jerk upon the ring In. will open either hook and release the wire. Also, the end of the wire I may be secured in any suitable manner, as by soldering or welding, directly to the shank, and the frangible connection formed in the wire itself by notching the wire just above the shank. I have already indi-' cated that when the indicator element is a fairly stiff wire the frangible connection need not be used, but I prefer to use such a connection with all forms of indicators, since the pull necessary to break the connection serves to indicate that the rod is in good order and has not been tampered with. The frangible connection is very essential where the indicator is formed of a highly flexible element such as a cord or a chain.

The internal grounding conductor 6 is provided to secure a better electrical connection between the head and the point of the rod than is afforded by the tube I, especially where the tube is an iron pipe, but it is obvious that the conductor 6 may be dispensed with and a fairly good ground obtained through the tube I alone. Also, where the tube l is formed of a copper-clad iron tube, the conductor 6 will not be needed.

In the appended claims, the term threadlike" is used in a broad sense to designate any of the forms of indicator element disclosed above. Also, the term frangible connection is used in a broad sense to designate any form of re- 15 leasable connection of the indicator element to the lower end of the rod.

What I claim is:

1. In a ground rod, the combination of a conducting tube having a driving point at one end and a driving head at the other, a depth indicator element arranged within said tube and having a frangible connection to said tube near the point end thereof and extending out of said tube near the head end.

2. In a ground rod, the combination of a conducting tube, a driving point closing one end of said tube, a driving head closing the other end of the tube, and a depth indicator within said tube extending substantially the entire length thereof and being removable through the wall of said tube near said driving head.

3. In a ground rod, the combination of a tube, a driving point closing one end of said tube, a driving head closing the other end of the tube, an indicator wire arranged within said tube, a frangible connection securing one end of said wire to said driving point, and the other end of said wire extending out of the wall of said tube near the driving head.

4. In a ground rod, the combination of a tube, av driving point closing one end of said tube, a driving head closing the other end of the tube, and a thread-like indicator arranged within said tube and having a frangible connection with said driving point, the free end of said indicator extending out of said tube through a hole adjacent said driving head.

5. In a ground rod, the combination of a tube, a driving point closing one end of said tube, a grounding conductor arranged within said tube and connected to said driving point, a tapered split-plug arranged within the open end of said tube and embracing the upper end of said grounding conductor, a driving head provided with a sleeve telescoping the upper end of said tube, said driving head being arranged to force said split plug into the end of said tube, thereby expanding the end of said tube and locking the same within said sleeve and clamping the upper end of said grounding conductor within said split plug.

6. In a ground rod, the combination of a tube, a driving point having a shank secured in one end of said tube, a grounding conductor arranged within said tube and connected to the shank of said driving point, a tapered split-plug arranged within the open end of said tube and embracing the upper end of said grounding conductor, a driving head provided with a bore for receiving the upper end of said tube, said bore having an enlarged recess adjacent the bottom thereof, and the bottom of said bore being arranged to force said split-plug into the end of said tube, expand the same into the recess, and thereby clamp together said grounding conductor, tube and driving head.

'7. In a ground rod, the combination of a tube, a driving point closing one end of said tube, a driving head closing the other end of the tube, a grounding conductor arranged within said tube and connected between said point and head, and a depth indicator within said tube extending substantially the entire length thereof and being removable through the wall of said tube near said driving head.

8. In a ground rod, the combination of a tube, a driving point closing one end of said tube, a driving head closing the other end of the tube, a grounding conductor arranged within said tube and connected between said point and head, and a thread-like indicator arranged within said tube and having a frangible connection with said driving point, the free end of said indicator extending out of said tube through a hole adjacent said driving head.

9. In a ground rod, the combination of a tube, a driving point having a shank secured in one end of said tube, a grounding conductor arranged within said tube and connected to the shank of said driving point, a tapered split-plug arranged within the open end of said tube and embracing the upper end of said grounding conductor, a driving head provided with a bore for receiving the upper end of said tube, said bore having an enlarged recess adjacent the bottom thereof,said driving head serving to force said split-plug into the end of said tube by impact thereon, whereby the tube is expanded into said recess and said conductor is clamped to said tube and head, an indicator wire arranged within said tube, and a frangible link connecting one end of the indicator wire to said shank, the free end of said Wire extending out of said tube at a point adjacent said driving head.

10. In a ground rod, the combination of a rod having a driving point at one end and and a driving head at the other end, and a threadlike depth indicator extending along said rod and having one end thereof secured to said rod near the driving point by a frangible connection.

11. In a ground rod, the combination of a rod having a driving point and a driving head, and a thread-like depth indicator extending along said rod and having one end secured to said rod near the driving point by a frangible connection, said rod being arranged to at least partly surround said indicator whereby the rod protects the indicator against mechanical injury while the rod is being driven into the earth.

ALBERT J. WAYMAN. 

